The present invention relates to an apparatus for measuring the temperature distribution or air velocity distribution of a print card equipped with a circuit component on a printed board in a state where it is mounted in a card rack.
The temperature of a component used for an electric appliance greatly affects the performance and reliability of the device.
As the temperature of the component increases, in most cases, the timing condition of a signal becomes strict, thereby attenuating the reliability of the component (the reliability lowers 1/2 for a temperature increase of 10.degree. C.).
Therefore, in order to attain the normal operation of a device and its reliability, a cooling apparatus and mounting apparatus must be adopted which can place all the components in a prescribed permissible temperature or lower (called "thermal design"). The measurement of temperature distribution of the print card in its state mounted in a sub-rack is an important test for verifying the thermal design.
In order to grasp the influence for temperature when the cooling fan suffers breakdown or a box structure has been changed partially, a technique for measuring the temperature distribution of the printed board in its mounted state in a real time is required.
FIG. 16 is a perspective view showing a technique for measuring the temperature distribution of a print card, as disclosed in e.g. the Unexamined Japanese Patent Application Publication No. Sho 50-104977.
In FIG. 16, reference numerals 1, 3, 4 and 5 denote a printed board equipped with circuit components, respectively. The intervals between the adjacent printed boards are set for the values when they are actually arranged on sub-racks. Reference numeral 6 denotes a plate of silicon (Si) or germanium (Ge) through which infrared can permeate. The interval between the plate 6 and printed board 1 is equally set for that between the printed board 1 and the other printed board which is to be arranged in front of it.
In front of the wafer 6, a thermal radiator video device such as a thermography device is arranged which can acquire the temperature distribution image of an object by detecting the infrared incident from the object.
An explanation will be given of the operation.
When power is supplied to the respective printed boards 1, 3, 4 and 5, the temperature of a print card of each printed board equipped with circuit components rises and becomes a stationary state after a predetermined time. As a result, the print card radiates infrared according to the temperature distribution of each print card.
After the infrared radiated from the circuit components of the printed board of such infrareds have permeated through the plate 6, they are detected by the thermal radiator video device 2. Therefore, the thermal radiator video device 2 can obtain the temperature distribution image of the print card of the printed board equipped with circuit components.
Generally, a plurality of sub-racks (card racks) equipped with a large number of print cards are stacked on a board of an electric appliance. Devices such as a power source and hard disk device and fan unit for cooling are also mounted on the board.
For the above electronic appliance, the method for measuring the temperature distribution of the above conventional print card has the following problems.
Basically, those other than the print cards at the ends provide a great error in the thermal environment. Where a plurality of sub-racks are arranged vertically, the thermal effect of the upper and lower sub-racks and for ventilation are not taken in consideration so that the state in which the print cards are actually mounted cannot be reflected.
The temperature distribution of the print cards at the ends in a mounted state can be measured in such a manner that a thin plate capable of permeating infrared is attached on a hole made in the board and side plate. Such a board and sub-rack with a hole are required for measuring the temperature.